Why SAN is Expensive
Storage area network, an architecture to remotely attach computer storage. SAN devices connect to a number of servers using fibre channel. Most SAN systems use the small computer system interface protocol. An add-on card must be installed in each computer that will be connected to
a SAN device. A SAN is seen by a connected server as a local drive. Since the SAN serves data only as raw disk blocks, the server itself must provide file management.
SAN protocols include Fibre Channel, iSCSI, ATA over Ethernet (AoE) and HyperSCSI.
A NAS is a single storage device that operate on data files.Typically makes Ethernet and TCP/IP connections.
Both NAS and SAN over come the limitations of the traditionally used Direct Attached Storage (DAS).NAS appears to the client OS (operating system) as a file server (the client can map network drives to shares on that server) whereas a disk available through a SAN still appears to the client OS as a disk, visible in disk and volume management utilities (along with
client’s local disks), and available to be formatted with a file system and mounted.
The hardware that connects workstations and servers to storage devices in a SAN is referred to as a “fabric.” The SAN fabric enables any-server-to-any-storage device connectivity through the use of Fibre Channel switching technology.